Medical tubing includes tubing used as stents, catheters, drain tubes, access ports, endoscope bodies and the like. The requirements for each type of medical tubing will depend on its use. For example, a medical tubing may need to be very flexible and yet pushable, or it may need to be thin-walled and yet, kink-resistant. Often, the tubing may require holes for drainage. The tubing may need to exhibit these properties in only specific regions.
Various methods have been described for manufacturing medical tubing. Most medical tubing is extruded from a single plastic material in a continuous forming process. While certain characteristics or variations may be imparted to the extruded tubing by altering the speed or the tension of the extruded material as it exits and cools from the extrusion machine, the variations are limited by the fact that a single material is extruded. Recent advances in extrusion technology have allowed the co-extrusion of multiple materials. This provides some usable variations in extruded tubing. Nevertheless, this is still a linear process and is still limited by the continuous flow of the extruded materials. Moreover, extrusion methods do not yield medical tubing having both very thin walls and high kink-resistance. However, it is relatively easy to add drainage holes to extruded tubing, for example, by drilling or puncturing where desired.
Recently, an alternative method for producing medical tubing has been described. For example, in U.S. Pat. No. 7,005,026, a method is described wherein a wire, coated with a plastic material, is wrapped around a mandrel forming a plurality of windings. The wound coated wire is then heated until the plastic material melts and bonds the windings to form a wire-reinforced sheath. See also U.S. Pat. No. 7,534,317, describing a method of manufacturing medical tubing by coating a mandrel with a first layer of plastic material to form an inner tube, placing a braid over the inner tube, placing a spring reinforcement over the braid, and then coating the braid with a second layer of plastic material to form an outer tube of a braid-reinforced sheath.
Medical tubing produced by these methods can be both thin walled and kink resistant, but it may be difficult to incorporate drainage holes, as care must be taken not to sever the wire/braid/spring reinforcement incorporated into the tubing. As the skilled practitioner will appreciate, a break in the wire reinforcement, whether the wire is formed from metal, plastic, or some other material, may reduce the column and/or hoop strength of the reinforced tube, and produce potentially hazardous broken ends. It may also produce undesirable debris or even projections or scars disrupting the outer surface of the tubing.
Accordingly, there is a need for medical tubing that is both thin walled and kink resistant and that includes drainage holes. There is further a need for a method of incorporating drainage holes into wire-reinforced tubing that avoids cutting or nicking the wire.